In a one chamber process multicrystalline silicon thin film solar cells with crystallites in the range of 10 to more than 100 pm were deposited on uncoated glass by Layered Laser Crystallization (LLC). During PECVD deposition of a-Si:H, laser crystallization was performed in the deposition chamber. A 400 nm thick seed layer simultaneously acting as transparent electrode was crystallized by scanning an Ar+-laser beam. Epitaxial thickening by applying repeated pulses of an KrF excimer laser was performed during further a-Si:H deposition. p(+)-p-n(+) cells with 3 mum thick absorber without. reflector and without antireflection coating showed V-OC = 425 mV, I-SC = 9.8 mA/cm(2), FF = 55%, and n = 2.3%.

Layered laser crystallization during PECVD of a-Si:H is a new and advantageous method to deposit c-Si films onto glass with a rate of 10 Angstrom s(-1). This new technology consists of two laser-induced crystal growth steps: A seed layer is prepared from a-Si:H by an overlapped scanning of an Ar+ laser beam. Then the seed is repeatedly thickened by melting of newly deposited a-Si:H on top of the c-Si with KrF laser pulses. Various deposition parameters were matched together to process a layer with crystallites 100 mum in size. p(+)pn(+)- or n(+)np(+)-junctions were deposited in one chamber and in one run. V-OC of 530 mV was achieved. (C) 2002 Elsevier Science B.V. All rights reserved.

By scanning a beam of a frequency doubled Nd:YAG laser a-Si:H thin films on fused silica or on glass were crystallized via melting. In this way polycrystalline films with crystallites several 10 lam in size throughout were obtained. The grain boundaries are mostly electrically inactive twin boundaries. By switching the scanned laser beam on and off periodically single crystalline patches 60 mum by 250 mum in size were prepared at predefined position. The crystallites are large enough for thin film transistors or MOSFETs to be placed entirely in single crystalline areas.

A technology is proposed to prepare crystalline silicon thin film solar cells on glass as a superstrate. In a first step an a-Si:H layer is deposited by PECVD onto borosilicate glass. By scanning an Ar/sup +/-laser beam, this layer is crystallized with grains several 10 /spl mu/m in size and is at the same time p/sup +/-doped by boron from the glass so that a transparent electrode layer is formed. In the next step further a-Si is deposited and repeatedly irradiated by an excimer laser during deposition. In this way, a p-absorber layer is grown epitaxially from the underlying electrode which is acting as a seed layer. Finally, by excimer laser doping, a n/sup +/-emitter is fabricated to result in a p/sup +/-p-n/sup +/-layer sequence. Onto the silicon, a metal is deposited as the second electrode acting as a back reflector. Results on the characterization of the different layers are presented with the emphasis on crystallographic and chemical properties. Challenges in preparing the proposed layer sequence are discussed.

During RF CVD of a-Si:H onto glass an Ar+ laser beam was scanned to crystallize a seed layer. Subsequently every 20 nm new deposited a-Si:H was molten by one light pulse from a KrF laser, so that the laser processing did not take any additional time. A highly conducting p(+) region close to the glass as transparent electrode and a p(+)pn junction within the film were deposited without a doping gas. REM, TEM images and XRD measurements confirmed an epitaxial growth of large crystallites. The self structured silicon/glass interface and film surface show increased scattering which supports light absorption. Transients of open circuit voltage after a pulsed generation by UV light at the p(+), as well as at the n side, were contactless sensed to evaluate the PV quality of films as deposited. A lifetime of more than 5 mus and a diffusion length for holes of more than 25 mum were determined.

Conditions for crystallizing a-Si:H films on glass substrates by laser methods are discussed. Special emphasis is given to crystallization procedures for thin film solar cells and for TFT's using Ar(+) or Cu vapor lasers. The properties of the resulting films such as grain structure, electrical properties, and impurity concentration is discussed.